1. Field of the Invention
This invention relates to a vehicle mounted tire pressure sensor which renders a visual readout of the pressure of each tire and enables the operator to inflate or deflate individual tires while driving the vehicle.
2. Description of the Prior Art
In the past few years, there have been several developments in the sensing of vehicle tire pressures. These developments have grown out of concern for the vehicle tires because not only can harm and destruction of the tire result from an under-inflated or over-inflated condition, but vehicle safety is also affected in that a low or blown tire can seriously affect the vehicle handling properties.
In the evolution of tire pressure sensing, there has resulted indicators mounted on each wheel and showing the tire pressure. A system of this type is shown in U.S. Pat. No. 3,961,309, High-Low Tire Pressure Signal Switch, issued on June 1, 1976. This patent is indicative of several that provide visual or other indications at the wheel that the tire pressure is out of a normal range.
There also has resulted the sensing of the tire pressure and the remote indication, preferably in the view of the driver, signaling an out-of-normal range condition. U.S. Pat. No. 3,977,355, Low Tire Pressure Warning System with Mechanical Latching, issued on Aug. 31, 1976 and U.S. Pat. No. 4,004,271, Low Tire Pressure Warning System, issued on Jan. 8, 1977 are indicative of these types of devices. With these devices however, only a low pressure warning signal is transmitted to the driver.
Another type of vehicle tire pressure detection system senses the temperature at the tire and generates a signal responsive to that temperature for providing an indication that the tire pressure is low. This system utilizes an electromagnetic transducer for generating a remotely detectable signal indicating low tire pressure. Positioned at a point separate from the wheel is a receiver which senses a change in a magnetic field and generates within the view of the vehicle operator a visual warning. An example of this type of device is shown in U.S. Pat. No. 3,852,717, Device for Automatically Detecting Abnormal Conditions in Vehicle Tires, issued on Dec. 3, 1974. Inductively coupled devices are used in U.S. Pat. No. 4,131,878, Detector for a Pneumatic Tire, issued on Dec. 26, 1978 and U.S. Pat. No. 4,148,008, Tire Pressure Monitoring System, issued on Apr. 3, 1979 to indicate that the tire pressure is out of a normal range. A Hall effect switch, stationarily positioned, detects the pressure responsive signal in U.S. Pat. No. 4,330,774, Tire Pressure Sensing System, issued on May 18, 1982.
Examples of radio signal transmitters positioned on the wheel for transmitting the pressure signal to the vehicle are described in U.S. Pat. No. 3,810,090, Pneumatic Tire Low-Pressure Monitoring and Warning System, issued on May 7, 1974; and U.S. Pat. No. 4,334,215, Continuous Heat and Pressure Surveillance System for Pneumatic Tires, issued on June 8, 1982.
As an extension of previous systems for detecting vehicle tire pressure, there has also evolved systems for releasing air from over-inflated tires such as shown in U.S. Pat. No. 4,330,774, Tire Pressure Sensing System issued on May 18, 1982. For replacing air in under-inflated tires during operation of the vehicle, the system shown in U.S. Pat. No. 4,067,376, Tire Pressure Warning System, which issued on Jan. 10, 1978 is described.
It is the purpose of the present invention to provide an improved system for detecting and signaling the tire pressure to the vehicle operator and for providing to the operator the capability for releasing air or supplying air to any of the vehicle tires to bring the pressure within desired operating limits.